DHCP server exhausts pool while leases free

November 2008


Problem

In order to get some information across to our VoIP phones, the DHCP server serves them an IP umber for a few minutes, after which they connect in a way independent from the DHCP server. Lately, some VoIP phones don't get connected any more, as reflected by unknown client lines in the DHCP logs.

[Note]Note

The unknown client messages to indicate that a client is unknown, which in DHCP parlance means that it doesn't have a host declaration. However, it seems that clients that don't have a host declaration (so the should get an unknonw client-line but are still going to get an address from a dnamic pool will not get an unknown-client line. So unknown client in the logs actually seems to serve as an indicator that a client is not going to be served.

/etc/dhcp3/dhcpd.conf Has been edited extensively lately, about a day prior to the first unknown clients. It now looks like:

shared-network MY-NET
{

#some options skipped for brevity"

set vendor-string = option vendor-class-identifier;
option NortelVoIPPhoneIdentifier code 128 = text;
option NortelVoIPVLANIdentifier code 191 = text;

class "VoIP" {
     match if option vendor-class-identifier = "Nortel-i2004-A";
}

subnet 172.29.66.0 netmask 255.255.255.0
        {

        authoritative;

        pool
                {
                allow members of "VoIP";
                deny known-clients;
                option routers 172.29.66.1, 172.29.66.2;
                option NortelVoIPVLANIdentifier "VLAN-A:824.";
                range 172.29.66.10 172.29.66.240

                default-lease-time 180;
                max-lease-time 300;

                }
        }
#rest of file skipped